Wear members in the form of adapters, shrouds, and the like are ordinarily secured to the front edge of an excavating bucket. Such wear members are commonly subjected to harsh conditions and heavy loading. Accordingly, the wear members wear out over a period of time and need to be replaced. The wear members are made to withstand the rigors of a digging operation and still be capable of replacement when worn. Whisler-style locking arrangements have long been in use for mechanically attaching wear members to the lip of a bucket. Such locks generally consist of a wedge and a C-shaped clamp or spool. While the wedge is typically hammered into the assembly, U.S. Pat. Nos. 4,433,496 and 5,964,547 disclose arrangements wherein the wedge is drawn into place under pressure from a screw. U.S. Patent Application Publication No. 2004/0216336 discloses a lock where the wedge is a conical threaded member that is turned to drive the wedge into and out of the assembly.
FIG. 19 discloses one example of a conventional Whisler shroud 21 attached to a lip 16. As seen in the drawing, the lip includes a digging edge 25, an inner surface 27 and an outer surface 29. A hole 31, which is elongated axially, extends through the lip at a location rearward of the digging edge. Hole 31 has a generally straight front wall 33 and a rear wall 35 that includes a step 37. The step includes a tapered surface 39 that tapers away from inner surface 27 as it extends rearward away from digging edge 25.
Shroud 21 wraps around the front end 25 of lip 16 with an inner leg 41 extending along inner surface 27 and an outer leg 43 extending along outer surface 29. Inner leg 41 includes an through-hole 47 which generally aligns with hole 31 when the shroud 21 is put on the lip. The hole 31 and opening 47 collectively define a passage 49 into which is received a lock 51 adapted to releasably hold the shroud 21 to the lip 16. Through-hole 47 includes a step 53 adjacent wear surface 55 of inner leg 41. As with step 37 in hole 31, step 53 includes a tapered surface 57 that tapers away from inner surface 27 as it extends rearward away from the digging edge 25. In this way, tapered surfaces 39, 57 diverge rearwardly at generally equal inclinations relative to a central axis of the lip 16.
Lock 51 includes a wedge 61 and a clamp or spool 63. Spool 63 has C-shaped configuration with a generally vertical body 65 and two axially extending arms 67, 69. Upper arm 67 is adapted to fit within step 53, while lower arm 69 is adapted to fit within step 37. Each arm 67, 69 is formed with an inclined inner wall 71, 73 that conforms and sets against a respective tapered surface 39, 57. The front surface of body 65 defines a ramp surface 75 that is inclined forward (relative to vertical) as it extends downward in passage 49. Wedge 61 has front and rear converging walls 81, 83. Converging wall 83 abuts ramp surface 75 during installation and use in order to produce a tight fit of lock 51 in passage 49. As shown in FIG. 19, converging wall 83 and ramp surface 75 are formed with interlocking ridges 85 to ensure a stable and sure contact between the surfaces.
For installation, shroud 21 is first fit on lip 16 so that through-hole 47 generally aligns with hole 31. Spool 63 is then placed within the defined passage 49 with arms 67, 69 inserted into steps 37, 53. On account of the incline of tapered wall 57 and inner wall 71, the spool tends to slide forward and downward through passage 49 if not held in place. As a result, the spool at times can slip through the lip and fall to the ground requiring the worker to retrieve it from under the bucket. This can be a difficult process particularly if installation is being done at night. In addition, crawling under the bucket can place the worker in a potentially hazardous position.
The spool 63 must therefore be held in place while the wedge 61 is inserted into the assembly. In order to withstand the rigors of the digging operation, the wedge must be fit very tightly into passage 49. A large hammer is required to install the wedge into the assembly, which places the worker in a potentially hazardous position for injury from pieces that may fly off during hammering.
As wedge 61 is forced into passage 49, arms 67, 69 are pushed rearward over tapered walls 39, 57. This causes shroud 21 to be pulled tight against digging edge 25 and inner leg 41 to be pinched against lip 16. This tight fit is intended to resist heavy and diverse loading that may be applied to the wear member. The large forces applied to the spool arms can result in spreading of the arms. Such spreading reduces the grip of the lock on the wear member and can at times lead to failure of the lock.